Sleeve augment device for an articulated joint

ABSTRACT

An augment device for a joint endoprosthesis, the device including a sleeve surrounding a channel extending through the sleeve. The sleeve is formed of porous material for ingrowth of bony material, the sleeve comprising an inner face and an outer face. The sleeve further comprises a wall surrounding the channel, the wall being made of solid material and forming a sandwich structure with the porous material, wherein the wall forms a bulkhead between the inner face and the outer face. Thereby, the bulkhead wall will stop inflow of any cement across the sleeve from its inner to its outer face. The porous material on the outer face will be kept free from cement and its capability to promote bone ingrowth is reliably preserved. The augment devices are preferably provided as a set having different sizes and straight or stepped bottoms for improved versatility and maximum preservation of natural bone matter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national phase patent application ofInternational Patent Application No. PCT/EP2016/064720, filed Jun. 24,2016, which claims priority to European Application No. 15176121.0,filed Jul. 9, 2015, which is hereby incorporated by reference in thepresent disclosure in its entirety.

FIELD OF THE INVENTION

The invention relates to an augment device for a joint endoprosthesis,and more particularly to a tibial augment for a knee jointendoprostheis.

BACKGROUND OF THE INVENTION

Due to diseases, injuries or wear, particularly due to high age,replacement of joints in a body, such as knee, shoulder, elbow, withendoprothetic implants is common. Due to other illness or due to anexplanting of a failed endoprosthesis it is not uncommon to find animplantation side for the endoprosthesis which is pathologic, mainly dueto bone defects in its vicinity. This is a problem for the surgeonssince a lack of strong bone near the joint implantation side couldrender implantation of the endoprosthesis impossible or could lead topremature failure. Since such bone defects are encountered quite often,various approaches to remedy the situation have been devised.

In particular for such indications, wherein a joint endoprosthesis is tobe used, it is known to provide an augmentation device which isconfigured to fill a gap left by defective bone. Such an augmentationdevice having the form of a sleeve is e.g. disclosed in U.S. Pat. No.8,506,645 B2. Accordingly, defective bone material will be removed andthe cavity created thereby will be filled by placing of the augmentdevice. The shape of sleeve serves a purpose of allowing the stem of astemmed endoprosthesis to pass through its central opening, which formsa channel for the stem. The sleeve itself is configured to be impactedinto the cavity.

It comprises a body formed with porous metal material for facilitatingbony ingrowth. However, preparing the site for reception of the augmentdevice in a precise manner is difficult. Whereas cement may be used tofill any gaps that may exist or to provide better seating for theaugment device in general, there is a problem that the cement enters theporous metal material, thereby rendering the desired ingrowth promotingcharacteristic rather useless. Further, such entering of cement wouldmake difficult any future removal of the augment device.

SUMMARY OF THE INVENTION

An augment device for a joint endoprosthesis, in particular a tibialaugment for a knee joint endoprosthesis, comprising a sleeve surroundinga channel extending through the sleeve from a top to a bottom of thesleeve, the sleeve being formed of porous material which is configuredfor ingrowth of bony material, the sleeve comprising an inner face andan outer face, the inner face defining the channel and a distancebetween the inner face and the outer face defining a thickness isaccording to the invention configured such that the sleeve furthercomprises a wall surrounding the channel, the wall being made of solidmaterial and forming a sandwich structure with the porous material,wherein the wall forms a bulkhead between the inner face and the outerface, the bulkhead being configured for blocking cement flow between theinner face and the outer face.

According to some embodiments, the sleeve includes a sandwich structure,the sandwich structure being a compound of a solid wall and the porousmaterial. By virtue of this, the solid wall will act as a bulkheadstopping inflow of cement across the thickness of the porous material.The cement may flow only so far until it reaches the bulkhead, and itwill be stopped there. Thereby it is avoided that the outer porousstructure is virtually filled with cement used in the channel, therebypreserving the bone ingrowth promoting effect of the porous materialbeing kept free from cement. As a further advantage, the solid wallserves as a reinforcing element which provides greater stiffness to thesleeve. The solid wall thus can serve at least two purposes, namelyfirst that of being a bulkhead protecting a portion of the porousmaterial against inflow of cement thereby preserving the desired boneingrowth capability of said porous material and further by providing agreater stiffness. These two advantages may be intertwined with eachother, particularly since the wall provides some reinforcement allowinga higher degree of porosity for even more improved bone ingrowthcapability, without compromising mechanical stability. This provides aunique, advantageous combination.

The wall may be positioned at the inner face. Thereby, the porousmaterial will be completely placed on the outside, providing full boneingrowth capability to the surrounding bony material. Optionally, porousmaterial will be placed on the interior side, too. Alternatively, araised structure having embossments may be placed on the inner face ofthe wall, thereby providing an improved bonding surface for cementapplied within the channel and facilitating removal as opposed to thevariant having porous material on the inner face.

The porous material is preferably of a high porosity (e.g. total porousvolume at least 60%-90% of total volume) and comprises interconnectedpores. Owing to such a high porous structure ingrowth of bony materialwill be highly facilitated.

Preferably, the wall extends along an entire height from the bottom ofthe top to the sleeve. Thereby it forms a complete bulkhead reachingover the entire device, shielding the complete inner space from anycement influx from the outside. This can be further improved byproviding a top cover made of solid material which is configured suchthat it covers essentially the complete top of the sleeve. The augmentdevice is thereby also protected against influx of cement from above. Itis further preferred to form the top cover and the wall as a unitaryelement. Thereby a complete bulkhead is formed, protecting againstinflux from the outer face as well as from a top.

Preferably, the augment device features a conical form such that itstotal width is tapering down towards its bottom end. It is preferablyconfigured such to be wider at its top and to have a cone angle between10° and 45° (measured as an imaginary apex angle). However, the conicform does not need to be perfect. In fact, it is preferable that thesleeve comprises at least one interior recess. Such an interior recessprovides additional space for accommodating a stem of theendoprosthesis, including any ribs that may be located on the stem orany other projection which may be present on the outer circumference ofthe endoprosthesis which otherwise could come in conflict with the innerface and/or top cover of the sleeve. In order to maintain full bulkheadfunctionality, a top cover preferably comprises further at least oneextension cover which is configured to cover side faces and/or a bottomface of the interior recess. Further preferably, the top cover and theextension covers are connected such as to provide a continuous topbulkhead. Optionally, the top cover, extensions and the porous materialmay be formed as a unitary element. Thereby, even in the case ofproviding such recesses the full bulkhead functionality of the wall andthe top cover will be preserved.

Preferably the edges of the sleeves are at least partly rounded and/orbevelled. Thereby it blends more easily into its cavity of the bone towhich it is to be implanted. Further, it provides less of a cuttinghazard for the surgeon in handling the augment device.

Preferably a raised structure having embossments is formed on the innerface. Thereby, the inner face will become non-smooth, thereby providinggreater friction between any cement applied in the channel and the wall.Due to the depressed nature of the embossments a light interlockingeffect may be achieved, however this effect will be small enough to beeasily overcome in case a removal of the augment device shall beperformed. Preferably, the embossments are groovings which arepreferably oriented in a direction pointing from the bottom to a top ofthe sleeve. By virtue of this, the cement applied in the channel blocksany unwanted sideways movement relative between the cement and theaugment device. However, owing to the orientation of the groovingsrunning from the bottom to the top any removal is facilitated, sincesuch a removal would be done by moving the augment device in saiddirection. This effect can be even more pronounced if the groovings areconfigured such as to be tapering in width. However, otherconfigurations could be chosen for the raised structure with itsembossments. Another preferred embodiment is having the embossmentsarranged in a matrix like fashion, wherein the individual embossmentsare preferably configured to have a checkered or diamond structure.Alternatively or additionally, a lattice structure is provided, thelattice structure comprising laths and interspaces. Interspaces areconfigured such as to be filled by the porous material, whereas thelaths provide additional structure reinforcement and thereby achieve animproved bonding of the porous material to the wall. The laths may beseparate elements, but it is preferred that they are formed unitary withthe wall.

In a particularly preferred embodiment, the sleeve comprises at leastone bending joint, the bending joint being configured for compressingthe channel. Further preferably, two or more bending joints are arrangedin a mirror symmetric fashion. Due to the bending joints the sleeve maybe compressed from the outside and will achieve a decreasedcircumference and width, enabling it to be put into a tight cavity ofthe bone more easily. Since the cavity is often dimensioned to be rathertight for improved mechanical stability of the augment device and theendoprosthesis in the bone, and further to preserve as much of healthybone as possible, there is a problem that forcing the augment deviceinto a tight cavity may create a risk of creating cracks in the bone. Byvirtue of the bending joints, rather than cracking the bone the sleeveitself will compress itself to a smaller size, thereby allowing it to bemore easily placed into the cavity without the risk of crackingsurrounding bone material. In a preferred embodiment, the bending jointis formed by a void in the sleeve, wherein a strip of solid materialspans the void. Preferably, the strip is oriented such as to be obliquewith respect to the wall, further preferably such that a lower end ofthe strip is positioned closer toward the outer face than an upper endof the strip which is positioned closer toward the inner face. The stripacts as a hinge providing the degree of movement required for bending apart of the sleeve in respect to the other part. Further, an axis of thehinge as formed by the strip is defined by the orientation of the strip.Rather than orienting the strip to parallel to a middle chord of thewall, it is oriented oblique to it. Thereby the bending access will notbe parallel to the plane of the wall, instead it will be parallel or atleast nearly parallel to a center axis of the channel. The degree ofoblique orientation is defined by the cone angle of the sleeve. In otherwords, the oblique arrangement of the strip counteracts the effect ofthe conically formed wall and ensures a compressing in a horizontalplane parallel to the top cover.

In a further preferred embodiment, the strip is configured to have areduced bending stiffness in a lower portion, preferably by means of atapering width. Owing to the lower bending stiffness the contribution ofthe lower portion to the overall bending stiffness is rather small. As aresult, the percentage reduction of the stiffness of a shorter bendingjoint is smaller than the percentage reduction of the length of thatbending joint where all bending joints—although having differentlengths—end at the top of the sleeve, e.g. at a sleeve having a steppedbottom.

Further preferably, the sleeve comprises a compensator elementconfigured for adjusting a circumference of the sleeve in a bended stateof the bending joint. The compensator element allows a degree of freedomfor absorbing a reduction of the circumference which will be realized bymoving the bending joints under compressive force. Preferably, thecompensator element is configured as at least two overlapping tonguesbeing in sliding relationship. Owing to the sliding relationship, thetongues maintain the bulkhead functionality even in the area of thecompensator element. Further, the sliding relationship allows a variancein length and thereby the reduction of the circumference.

In a preferred embodiment a plurality of small holes are provided in thewall. The term “small holes” is to be construed such that the holes havea diameter being so small that it blocks cement from passing throughsaid holes. Thereby the bulkhead functionality in respect to cement ispreserved. However, the presence of the small holes further improvesbone ingrowth and, more importantly, serve as aeration holes ventingpockets of trapped air which may otherwise be formed between the innersurface of the wall and inflowing cement. By virtue of the small holesair can escape more easily thereby implantation with cement isfacilitated and made more reliable.

Further, windows may be provided in the wall, preferably arranged in arow close to the top. Further preferably, the windows are extendingthrough the porous material, too. The windows form deliberate openingsfor the cement, such that the cement place on an internal side may passthrough the windows towards the outer side in a controlled manner.Thereby unwanted distribution of cement is kept controlled. By allowingthe cement to flow through the windows results in the cement formingpin-like projections reaching through the windows, thereby arresting theposition of the augment device like fixation pins. This provides for animproved fixation. Further, by positioning the windows close to the topthese fixation pins may be easily cut in case of a removal of theaugmentation device. Additionally or as an alternative, a largepassageway is provided in the wall and the porous material, therebyextending through entire sleeve. The passageway is orientatedperpendicular to the channel. Preferably, the passageway is positionedin a middle portion of the wall. Further preferably, the passagewayfeatures rounded corners for improved resistance against cracking. Byvirtue of the passageway, a rather large fixation trunnion is formed byallowing cement flow through it in a controlled manner, and providing avery solid fixation trunnion. The term “large” is to be construed suchas to mean a cross-section area that is at least three times the area ofa single window.

The augment device may have a flat bottom surface. However, preferablyembodiments are provided which are having a stepped bottom surfacehaving two sections, one section in which the augment device has itsfull height and another section where it has a reduced height.Preferably the bottom is stepped such that the height in the reducedportion is about 0.4 to 0.7 of the full height. Further preferably, atransition between the section with full height and the section withreduced height is in the middle of the sleeve along a line of thesymmetry, dividing the sleeve in a left and a right part. However, thattransition may be offset to either side if so desired.

According to a further embodiment of the invention, a set of augmentdevices as defined above are provided, wherein the set comprises a firsttype of augment devices having a full height and a second type ofaugment devices having a reduced height, wherein the reduces height ispreferably 0.4 to 0.7 of the full height.

Further preferably, the set comprises a third type which has a steppedbottom surfaces. Further preferably, the set comprises the said types indifferent sizes, preferably ranging from small over medium to large.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described according to theaccompanying drawing in an exemplary manner. In the drawings:

FIGS. 1 a, b are perspective views of a first exemplary embodiment;

FIG. 2 is a schematic view showing an augment device according to theinvention in situ;

FIG. 3 is a cross section of the embodiment depicted in FIG. 1;

FIG. 4 is a detailed view of a wall of the augment device;

FIG. 5 a, b are perspective views of a second and third embodimenthaving windows and a passageway, respectively;

FIG. 6 a-c are detail views showing a raised structure on an inner face;

FIG. 7 is a top view of a fourth embodiment having bending joints;

FIG. 8 is a detailed cross section trough one of the bending joints; and

FIG. 9 shows a set of augment devices of different types.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of an augment device 1 according to the presentinvention is shown in FIGS. 1-4. The augment device 1 of this embodimentis preferably a tibial augment which is made of a biocompatible metallicmaterial. It is preferably selected from a group comprising titaniumalloys, pure titanium, cobalt chromium, stainless steel, tantalum andzirconium. Further preferably, the material is pure titanium (forexample Ti Grade 2). This combines excellent biocompatibility with goodstrength and stiffness characteristics. Another preferred material is atitanium alloy (for example Ti6Al4V). This material is more regularlyavailable, and also it has a higher stiffness.

The tibial augment has a generally conic form of a sleeve 10. The sleeve10 surrounds a channel 11 which runs entirely through the augment device1 from its top 12 to its bottom 13. The channel 11 is configured forreceiving a stem of an endoprosthesis, in particular the stem 94 of atibial part 92 of a knee prosthesis 9.

The sleeve 10 is made in a sandwich configuration having a wall 3combined with two layers of porous metal material 2. It is to be notedthat the porous portion at the inner face is optional; alternativeconfigurations are shown in FIG. 6 a, b, c. The wall 3 runs from thebottom 13 to the top 12 of the sleeve 10 surrounding completely thechannel 11. On the top 12 the wall 3 meets a top cover 4 which covers acomplete top side 12 of the sleeve 10. The top cover 4 and the wall 3form a unitary piece. Thereby, the wall 3 in conjunction with the topcover 4 act as a bulkhead blocking any passage of cement from thechannel 11 to an external side of the sleeve 10.

The tibial augment 1 is configured such as to be anatomically sized andshaped to fill a cavity in an upper part of a distal bone 99, namely thetibia. The augment device 1 is formed generally conically for betterfitment. Its bottom side 13 is generally planar as well as its top 12.

As can be appreciated in FIG. 2, the augment 1 is placed in the cavityof an upper portion of the bone 99, thereby forming a base on which atibial plate 93 of the tibial component 92 of the knee prosthesis 9 isto be positioned. The knee prosthesis 9 further comprises a femurcomponent 91 configured for rotatable interaction with the tibialportion 92. The tibial component 92 further comprises a stem 94configured to be anchored in a medullary channel of the tibia 99. Thestem 94 is routed through the channel 11 of the tibial augment 1. Inorder to provide sufficient room for any ribs 94′, or other projectionson the stem 94 or the tibial part 92 generally, the tibial augment 1 isfurther provided with recesses 16 in order to provide additional roomfor the stem 94 and its projections 94′. The recesses 16 may beconfigured like depressions as depicted in FIG. 3, having a bottom face16″ and side face 16′. In order to provide a continuous top bulkhead,the bottom face 16″ and the side face 16′ is closed by an extensioncover 45 which functions as an extension of the top cover 4. Thereby, acontinuous bulkhead on the top side is achieved, thereby avoiding anyunwanted leakage of cement trough the recesses 16.

A porous material 2 placed on the outer face of the wall 3 is preferablya highly porous material having a degree porosity of at least 60-90%.Further, the pores are interconnected and elementary cells defining thepores are arranged in a regular order. The interconnected pores providefor a much improved ingrowth of bony material, and thereby ensure a goodstabilization of the tibial augment 1 in the tibial bone 99.

Examples for alternative embodiments of the inner face are shown in FIG.6a-c . FIGS. 6a and 6b show the inner face without and FIG. 6c with aporous portion on the inner face, however it is to be noted that theporous portion is entirely optional and either embodiment may beprovided with or without it. In these embodiments the inner face isprovided with a raised structure 61 having embossments 62 there between.In a first variant shown in FIG. 6a , the embossments 62 are configuredto have a diamond shape and to be arranged in a matrix like fashion.This provides for additional fixation in both, horizontal as well asvertical direction. In FIG. 6b a variant is shown having the embossmentsconfigured as groovings 62′, the groovings 62′ being oriented to run ina direction form the bottom to the top of the sleeve 10. This providesfor an improved fixation effect in respect to a horizontal direction,but allows for a facilitated removal of the augment device in a verticaldirection. In FIG. 6c a variant is shown having a lattice structure 6provided on the inner face. The lattice 6 comprises laths as raisedstructure 61 and interspaces 62″ as embossments. The laths 61 define agrid, with the interspaces 62″ being arranged there between. Theinterspaces 62″ are configured to be optionally filled by the porousmaterial 2, preferably such that it will be flush with the surface ofthe laths 61 in a filled state. The lattice structure 6 enhancesfixation and has a considerable reinforcing effect on the sleeve 10,thereby providing addition mechanical strength.

For implantation, cement may be applied for fixation of the stem 94. Forthis reason, the cement will be applied within the channel 11 around thestem 94. The cement may flow into the porous material 2 placed on aninner face of the wall 3, thereby providing a strong, interlockedbonding. However, in order to preserve the positive bone ingrowth effectof the porous material 2, the cement shall not reach the outer face. Forthis purpose the wall 3 is provided acting as a bulkhead confining thecement to an inner portion, thereby keeping the outer face essentiallycement-free. The top cover 4 ensures that no cement could spill overtowards the top. A bottom cover is not necessary. However, it may beprovided at the section of the bottom outward of and including the wall,thereby blocking any unwanted influx of cement in the porous material 2on the outer face.

In order to allow a smooth influx of the cement into porous material 2on the inner face it is necessary to remove air displaced by the cementfrom the inner portion. In order to facilitate removal of air in orderto avoid the air being trapped, a plurality of small holes 32 areprovided in a regularly arranged manner at the wall 3, preferably at theentire wall 3. This is depicted in FIG. 4. The size of the holes 32 isdimensioned such as to allow passage of gases like air, but has to blockany passage of a cement. A preferred size is between 0.3 to 0.5 mm.

Now referring to FIG. 5, second and third embodiments are shown beingprovided with additional means for fixation. To this end, windows 34 areprovided in a row close to a top end of the sleeve 10. The windows 34configured such as to penetrate the wall 3 and preferably the porousmaterial 2 on either side. Upon implantation and application of cement,the cement flows freely through the windows 34 from the channel 11outwards to the exterior. Since that flow of cement is confined to thevicinity of the windows 34 no adverse effect are encountered withrespect to promoting bone ingrowth capability of the porous material 2on the outer face. Yet, the cement flowing through the windows 34 actslike additional fixation pins securing the tibial implant 1 into itsplace. This allows for a better and considerable faster fixation of theaugmentation device 1. A further advantage of this configuration is,that in a case of a required removal of the augment device 1 the cementpins reaching through the windows 34 could be easily cut from theoutside owing to the proximity of the windows 34 to the top 12 of thesleeve 10. Thereby any removal will be facilitated by maintaining thehigh degree of stabilization during implantation.

Additionally or alternatively, as depicted in figure in 5 b, a ratherlarge passageway 36 can be formed in a more central area of the sleeve10. The passageway 36 runs through the wall 3 and the porous material 2.The passageway 36 is oriented essentially perpendicular to a center axisof the channel 11. The dimension of the passageway 36 through the wall 2a is selected such that it has more than three times the area of any ofthe windows 34. Thereby, by flowing of cements trough the passageway 36a rather massive trunnion for additional fixation strengths will beformed. Similarly as explained above in respect to the windows 34, thisadditional fixation could be rather easily removed in case of a removalby cutting of the cement trunnion. In the depicted exemplary embodimentthe passageway is dimensioned to be 10×8 mm.

A further embodiment is shown in FIGS. 7 and 8. This embodiment featurestwo sets of bending joints 7, 7′. The bending joints allow a bending ofthe sleeve 10 such that it will be compressed as a whole, therebyreducing the size of the channel 11 and the outer dimension of thesleeve 10. The bending joints 7, 7′ is formed by a void 17 in the sleeve10 combined with a metal strip 71 which spans the void 17. As bestappreciated in FIG. 8, the metal strip 71 is of solid material and runsfrom a top 12 to a bottom 13 of the sleeve 10. The strip 71 is orientedoblique with respect to the wall 3 such that a lower end 73 of the strip71 is positioned closer toward the outer face of the wall 3 and theupper end 72 of the strip 71 is placed closer to the inner face of thewall 3. By virtue of this arrangement, the strip 71 is orientedessentially parallel to a center axis of the channel 11. Thickness ofthe strip 71 at a lower portion 74 is reduced. To this end, the strip 71is configured such as to have a tapering width towards its lower end 73.By virtue of this tapering, the most bending force will be created bythe upper part of the strip 71, whereas the lower portion 74 will onlycontribute to the bending force to a much lesser degree.

The bending force and movement effected thereby is depicted with respectto FIG. 7. Two pairs of bending joint 7, 7′ are provided in a mirrorsymmetric configuration. A first set of bending joints 7 is placed at arear wall of the sleeve 10. By exerting a bending force, the bendingjoints 7 allow for a movement in a rotational direction as indicated bythe single arrow. Thereby an axis of bending defined by the bendingjoints 7 provides for an elasticity in a medio-lateral (ML) direction.

A second set 7′ is provided which is arranged in a mirror symmetricconfiguration at the side portion of the sleeve 10. The bending joints7′ provide a range of motion as depicted by the double arrow. Thisprovides for an axis of bending which gives anterior/posterior (AP)elasticity. As a result, by providing both pairs of bending joints 7, 7′compressibility in two dimensions is achieved, namely one in MLdirection and another in AP direction.

By exerting bending force the width of the inner channel will bereduced. Thereby, its circumference will be reduced. In order to enablethe sleeve 10 for such a reduction, a compensator element 8 is provided.In the depicted embodiment (see FIG. 7) it is arranged at an opposite,front side of the sleeve 10 to the bending joints 7. The compensatorelement is comprised of two tongues 81, 82 arranged at a left and aright portion of the sleeve 10. The tongues 81, 82 are arranged in anoverlapping configuration, leaving just a tiny gap 83 there between. Thetongues 81, 82 slide along each other under the effect of a bendingmotion with the bending joints 7, 7′. The gap 83 is dimensioned such asto small enough to block leakage of cement.

The bottom 13 of the augment device 1 may be flat or stepped (see FIG.9). In the stepped variant, a portion 13′ with a reduced height ispresent on either the left or the right side. A transition surface 19connects the portion with full height with the portion 13′ having areduced height.

Further, additional types are provided that have a reduced height overthe entire area. This type is depicted as type 1′ in FIG. 9. The typehaving the stepped bottom is depicted as type 1″ whereas the originaltype as depicted in FIG. 1-8 is shown as type 1 in FIG. 9.

Preferably, a full set of augment devices is provided. The setcomprising the types as mentioned above. Additionally, the types areprovided in different sizes I, II, III and IV, with I being extra small,II being small, III being medium; and IV being large. This allows thesurgeon a rather broad range of options in order to select anappropriate augment device 1 depending on the actual conditions of theimplant site.

1. An augment device for a joint endoprosthesis, the device comprising:a sleeve surrounding a channel extending through the sleeve from a topto a bottom of the sleeve, the sleeve being formed of porous materialwhich is configured for ingrowth of bony material, the sleeve comprisingan inner face and an outer face, the inner face defining the channel anda distance between the inner face and the outer face defining athickness, and a wall surrounding the channel, the wall being made ofsolid material and forming a sandwich structure with the porousmaterial, wherein the wall forms a bulkhead between the inner face andthe outer face, the bulkhead being configured for blocking cement flowbetween the inner face and the outer face.
 2. The augment device ofclaim 1, wherein the wall is located at an inner position such that itforms the inner face of the sleeve.
 3. The augment device of claim 1,wherein the wall is located at an intermediate position along adirection of the thickness such that the porous material is formed on aninward facing side and an outward facing side of the wall.
 4. Theaugment device of claim 1, wherein the sleeve is of a generally conicalshape.
 5. The augment device of claim 1, wherein further comprising atop cover made of solid material, wherein the top cover covers thecomplete top of the sleeve.
 6. The augment device of claim 5, whereinthe top cover and the wall form a unitary element.
 7. The augment deviceof claim 5, wherein the sleeve comprises at least one recess and the topcover further comprises at least one extension cover which is configuredto cover side faces or a bottom face of the recess.
 8. The augmentdevice of claim 7, wherein the top cover and the extension cover areconnected such as to provide a continuous top bulkhead.
 9. The augmentdevice of claim 1, wherein edges of the sleeve are at least partlyrounded, at least partly beveled, or at least partly rounded andbeveled.
 10. The augment device of claim 1, wherein a raised structurehaving embossments is formed on the inner face.
 11. The augment deviceof claim 10, wherein the embossments are groovings.
 12. The augmentdevice of claim 11, wherein the groovings are tapering in width.
 13. Theaugment device of claim 10, wherein the embossments are arranged in amatrix.
 14. The augment device of claim 10, wherein the raised structurewith embossments is configured as a lattice structure comprising lathsand interspaces.
 15. The augment device of claim 14, wherein the lathsare formed unitary with the wall.
 16. The augment device of claim 1,wherein the wall includes a plurality of small holes.
 17. The augmentdevice of claim 1, wherein the wall includes windows.
 18. The augmentdevice of claim 17, wherein the windows extend through the wall and theporous material.
 19. The augment device of claim 1, wherein a passagewayis provided which is oriented to run across the channel, the passagewayextending through the entire sleeve.
 20. The augment device of claim 1,wherein the sleeve comprises at least one bending joint, the bendingjoint being configured for compression of the channel.
 21. The augmentdevice of claim 20, wherein the bending joint is configured to have alower bending stiffness in a lower portion than in an upper portion. 22.The augment device of claim 20, wherein the sleeve comprises acompensator element configured for adjusting a circumference of thesleeve in a bended state of the bending joint.
 23. The augment device ofclaim 1, wherein the sleeve has a stepped bottom formed by a firstportion having full height and a second portion having reduced heightthat is less than the full height.
 24. The augment device of claim 23,further comprising a transition at a step between the full height andthe reduced height, the transition defining a left and a right half ofthe augment device.
 25. A set of augment devices comprising the augmentdevice of claim 1, wherein a first type of the augment device has a fullheight and a second type of the augment device has a reduced height witha planar bottom, wherein the reduced height is less than the fullheight.
 26. The set of claim 25, wherein the set includes a third typeof the augment device, the third type having a stepped bottom.
 27. Theset of claim 25, wherein the set comprises different sizes of the twotypes.
 28. The augment device of claim 1, wherein the augment device isa tibial augment for a knee joint endoprosthesis.
 29. The augment deviceof claim 4, wherein the sleeve is wider at its top and has a cone anglebetween 10° and 45°.
 30. The augment device of claim 7, wherein the atleast one extension cover is configured to cover the side faces and thebottom face of the recess.
 31. The augment device of claim 11, whereinthe groovings are oriented in a direction pointing from the bottom tothe top of the sleeve.
 32. The augment device of claim 10, wherein theembossments are arranged in a checkered or diamond structure.
 33. Theaugment device of claim 14, wherein the porous material fills theinterspaces.
 34. The augment device of claim 17, wherein the windows arearranged in a row adjacent to the top of the sleeve.
 35. The augmentdevice of claim 19, wherein the passageway is positioned in a centralportion of the wall.
 36. The augment device of claim 20, wherein thesleeve comprises two or more bending joints arranged in mirror symmetry.37. The augment device of claim 22, wherein the compensator element isconfigured as two overlapping tongues arranged in a slidingrelationship.
 38. The augment device of claim 23, wherein the reducedheight is about 0.4 to 0.7 of the full height.
 39. The set of augmentdevices of claim 25, wherein the reduced height is about 0.4 to 0.7 ofthe full height.